Merge pull request #3442 from edx/adam/fix-template-error

fixes templating error (LMS-2560)

lms/templates/static_templates/server-error.html

@@ -4,7 +4,7 @@
 <section class="outside-app">
   <h1>
     ${_(u"There has been a 500 error on the {platform_name} servers").format(
-        platform_name=u"<em>{}</em>".format(platform_name=settings.PLATFORM_NAME)
+        platform_name=u"<em>{platform_name}</em>".format(platform_name=settings.PLATFORM_NAME)
     )}
   </h1>
   <p>